On Mon 06-10-14 21:10:25, Heinrich Schuchardt wrote: > On 06.10.2014 16:12, Jan Kara wrote: > >On Fri 03-10-14 10:19:30, Heinrich Schuchardt wrote: > >>The fanotify and the inotify API can used to monitor changes of the file > >>system. > >> > >>System call fallocate modifies files. Hence it should trigger the corresponding > >>fanotify (FAN_MODIFY) and inotify (IN_MODIFY) events. > >> > >>This patch adds the missing call to fsnotify_modify. > > Well, there are different fallocate() commands and e.g. pure > >FALLOC_FL_KEEP_SIZE call will not change any data in the file. I'm not sure > >how much we care but I wanted to point that out... > > The most interesting case is FALLOC_FL_COLLAPSE_RANGE because this > value allows to create arbitrary file content from random data. > Hence I think we really need to create FAN_MODIFY in this case. > > As the fallocate(2) man page teaches: > After a successful call, subsequent writes into the range specified > by offset and len are guaranteed not to fail because of lack of disk > space. > > So calling fallocate(fd, FALLOC_FL_KEEP_SIZE, offset, len) may > result in different outcomes of a subsequent write depending on the > values of offset and len. > > Calling fallocate for a region already zeroed will not result in any > data change. > > I would like to compare fallocate() with write(). > > When we call write() we always create a FAN_MODIFY event even in the > case of overwriting with identical data. > > So event FAN_MODIFY does not provide any guarantee that data was > actually changed. > > In analogy to write() I suggest to keep the logic for fallocate() as > trivial as possible: > If fallocate() succeeds, create IN_MODIFY and FAN_MODIFY events. OK, makes sense. You can add: Reviewed-by: Jan Kara <jack@xxxxxxx> Honza > >>Signed-off-by: Heinrich Schuchardt <xypron.glpk@xxxxxx> > >>--- > >> fs/open.c | 5 +++++ > >> 1 file changed, 5 insertions(+) > >> > >>diff --git a/fs/open.c b/fs/open.c > >>index d6fd3ac..03aa8e5 100644 > >>--- a/fs/open.c > >>+++ b/fs/open.c > >>@@ -295,6 +295,11 @@ int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len) > >> > >> sb_start_write(inode->i_sb); > >> ret = file->f_op->fallocate(file, mode, offset, len); > >>+ > >>+ /* Create inotify and fanotify events. */ > >>+ if (ret == 0) > >>+ fsnotify_modify(file); > >>+ > >> sb_end_write(inode->i_sb); > >> return ret; > >> } > >>-- > >>2.1.0 > >> > -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
